1. Technical Field
The present invention relates to a projector.
2. Related Art
As an apparatus capable of displaying an image for a large screen, there is a commercially available projector in which a small light modulation device for forming an optical image in accordance with image information is illuminated with light from a light source apparatus and the optical image is enlarged and displayed through a projection lens on a screen or any other suitable surface.
In recent years, it has been increasingly desired to reduce the size of a projector so that, for example, an enlarged image can be displayed in unspecified locations. To achieve the size reduction, reduction of the size of each member used in a projector has been underway in a variety of forms, and as one of them, an illuminator that can be reduced in size without significant reduction in the amount of output light has been studied. JP-A-2003-16802 proposes an example of the technology described above.
JP-A-2003-16802 proposes an illuminator including halved primary and secondary reflection mirrors. That is, a typical reflection mirror having a reflection surface entirely surrounding an arc tube is cut in half along a plane parallel to the optical axis, whereby the size of the light source apparatus is reduced. On the other hand, a small secondary reflection mirror that reflects the light that is emitted from the arc tube but is not directly incident on the halved reflection mirror (primary reflection mirror) toward the primary reflection mirror is provided, whereby the light source apparatus is reduced in size while the amount of output light is maintained.
The technology described in JP-A-2003-16802 allows the light source apparatus to be reduced in size with the amount of light maintained, whereby a projector using the light source apparatus can be significantly reduced in size. The technology, however, still needs to be improved from the viewpoint of forming an excellent image by using the output light.
That is, in the illuminator described in JP-A-2003-16802, the primary reflection mirror has an asymmetric shape obtained by halving a typical primary reflection mirror entirely surrounding an arc tube. As a result, the illuminance distribution of the light reflected off the primary reflection mirror has non-uniformity in which the illuminance on the side far away from the arc tube is low, whereas the illuminance on the side close to the arc tube is high, which could result in brightness unevenness in which one end of an object to be illuminated is dark, whereas the other end thereof is bright.
When the illuminator described above is incorporated in a projector, a resultant projected image also suffers from brightness unevenness and decrease in image quality. In particular, in a three-panel projector in which the light from an illuminator is separated into red (R), green (G), and blue (B) three color light fluxes, which are modulated by light modulation devices to form image light, which is then projected and displayed, it is conceivable to transmit one of the three color light fluxes through a relay optical system to the corresponding light modulation device (object to be illuminated), such as a liquid crystal panel. In this configuration, since an image formed by the light modulation device illuminated with the light having passed through the relay optical system is reversed with respect to the images formed by the other two light modulation devices, the brightness unevenness described above results in color unevenness and hence a decrease in display quality.